Fertilization facts for kids

Human sperm arrives at the egg cell.

Liverworts are a kind of small plant with a complex life cycle that includes fertilization. The sperm and the egg come together to make a zygote. The zygote grows into an embryo.

Fertilization (British English spelling: fertilisation) is when a male's sperm enters a female's ovum (or "egg"). Fertilization is also called conception. Biologists call a fertilized egg a zygote. A zygote grows into an embryo.

Fertilization occurs in animals, including humans and birds, in plants, fungi, protists, in fact all eukaryotes. Fertilization makes a cell with twice as many chromosomes. The eukaryote life cycle includes meiosis which divides the chromosome number in half.

In animals

In animals, there are two types of fertilization, internal and external. Internal fertilization happens in the female body. External fertilization happens outside of the body. Mammals, birds, and reptiles use internal fertilization. Amphibians and most fish use external fertilization. Some animals with internal fertilization give birth to live offspring. Others such as birds, most reptiles, and some mammals such as the Platypus, lay eggs.

Internal fertilization happens during mating. Sperm cells travel from the male testicles to the female uterus. One sperm attaches to the egg in the uterus. Together, they become a zygote.

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  Coral animals send eggs and sperm into the water separately. They are carried in the water currents and meet up to fertilize, and then grow into new coral animals.

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  Most fish fertilize their eggs externally. The eggs and sperm are put into the water at the same time.

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  Bird eggs are usually fertilized before they are laid. (In some birds and reptiles an unfertilized egg can still be laid, but it will never hatch.)

Related pages

• Alternation of generations
• Mating

Images for kids

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  In the Bryophyte land plants, fertilisation takes place within the archegonium. This moss has been genetically modified so that the unfertilised egg within the archegonium produces a blue colour.

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  Red-veined darters (Sympetrum fonscolombii) flying "in cop" (male ahead), enabling the male to prevent other males from mating. The eggs are fertilised as they are laid, one at a time.

See also

In Spanish: Fecundación para niños